Fluid activatable adhesives and fluids for activating same for use with liner-free labels

ABSTRACT

Fluid activatable adhesive compositions and activating fluid(s) for activating the adhesive composition are described herein. The adhesive compositions contain at least two polymers with different hydrophilicities. The hydrophilic polymer has quick tack when exposed to a hydrophilic solvent, such as water or other aqueous solvent, while the hydrophobic polymer provides strong adhesion to a paper or polymeric substrate. The adhesive composition may contain particulate fillers which enable fast exhaustion of the activation fluid out of the adhesive when applied to a substrate, thereby allowing the hydrophobic polymers of the adhesive composition to achieve strong adhesion of the liner-free label to the paper or polymeric substrate. The particulate fillers may also function as anti-blocking agents when liner-free label media are tightly wound in a roll. The adhesive compositions described herein may be used not only on paper, cardboard, and metal, but also on glass and plastics commonly used in commercial applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 13/294,438filed Nov. 11, 2011, which claims priority to U.S. Ser. No. 61/440,384entitled “Fluid Activatable Adhesives and Fluids for Activating Same forUse with Liner-Free Labels” filed Feb. 7, 2011, both of which are hereinincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to fluid activatable adhesives and fluidsfor activating the adhesives, particularly for use with liner-free orliner-less labels, capable of adhering to a variety of substrates, suchas paper or polymeric substrates.

BACKGROUND OF THE INVENTION

Label printing and/or labeling typically consists of label media whichinclude an adhesive composition layer that is constantly andconsistently tacky. Many of these label media are formed with aremovable non-stick layer, containing a release coat and a releaseliner, over the adhesive composition layer, to prevent the adhesivecomposition layer from coming into contact with internal components of alabel printer, applicator, or labeler and/or the printable layer of anadhesive sheet when an adhesive sheet is wound in a form such as a roll.

In some instances, the liner layer is disposed of after printing or atthe time the label is applied to an article, either manually or by anautonomous process designed for the removal purpose. The disposableliner layers create waste disposal issues.

In other instances, an adhesive label is formed by a sheet, having aprinted layer, a release coat, and an adhesive composition layer. Therelease coat prevents the adhesive composition layer from adhering tothe printed layer, but standard printing, labeling, and label applyingequipment must be coated with a non-stick material to prevent theadhesive composition layer of the adhesive label from gumming or jammingthe equipment components. Instead of covering an adhesive compositionlayer with a non-stick material, a printable layer of a label andinternal components of a label printer are coated with a non-stickmaterial to resist the adhesive composition layer of the label that isconstantly and consistently tacky. This technique requires theadditional step of coating components with a non-stick material, whichcan significantly increase costs.

Numerous attempts have been made to use conventional polymeric adhesivecompositions with tacky or pressure-sensitive adhesives (PSA) inliner-free label constructions where a non-stick or release layer iscoated onto the opposite side of the adhesive label. These are notcompatible in conventional labeling equipment, requiring specialliner-free label printers and application systems. In addition, thenon-stick top-coating greatly reduces the printability of the label. ThePSAs cause machine problems by gumming up label application systems andcreate cleanup issues. Other attempts have been made to make a dry-gumor water or solvent or co-solvent remoistenable adhesive label. Theseare typically based on both carbohydrate and synthetic polymericadhesives. These adhesives have little utility on many synthetic andnon-porous substrates as they do not form substantial adhesive ormechanical bonds to the substrate. These substrates are labels prone to“swimming” or moving from the desired application area duringdown-stream processing due to a lack in rapid bond formation. As such,these attempts have had little success.

Certain liner-free labels have been developed having a printed layer, asheet, and an adhesive composition layer that can be made tacky by anactivator prior to or after printing/applying an image. However, many ofthese embodiments still require a non-stick coating to avoid the gummingproblem discussed above, such as described in U.S. Pat. No. 6,298,894 byNagamoto et al. which disclose the use of silicone oil as a non-stickcoating. In addition, many of the activatable adhesive liner-free labelsare water activated and/or solvent activated. These labels lack bothstrong adhesion on polymeric substrates and quick tack to polymericsubstrates. These labels are also prone to “swimming” as discussedabove.

U.S. Pat. No. 7,943,714 describes adhesive formulations. The polymersused in the formulations having a high acid number, e.g., 100 orgreater. In the examples, the polymer solutions have a pH of 4 or less.Such highly acidic materials can be problematic. For example,hydrophobic polymers, which are typically formulated as emulsions, canbe stabilized at low pH. Moreover, polymers with high acid numbers areprone to crosslink. Crosslinking can create a material that resistspenetration of the activation fluid which can adversely affectperformance, such as quick tack and/or long term adhesion.

Each of the prior art systems discussed above presents differentdrawbacks. A non-stick liner layer is typically non-recyclable and notre-usable, thereby generating waste for every label that is used.Coating components with non-stick material increases the costs of thesystem and may not entirely prevent gumming of the system, which islikely to occur when an adhesive residue adheres to the labelprinter/applicator component.

It is therefore desirable to eliminate the need for an adhesive sheet tobe formed with a non-stick liner layer or for the labelprinter/applicator components to be coated with non-stick materials. Itis also desirable for a water-activated and/or solvent-activatedliner-free label to exhibit both quick tack to polymeric substrates andstrong adhesion on polymeric substrates.

Accordingly, it is an object of the invention to provide liner-freeadhesive labels and methods of making and using thereof, wherein thelabel is activated by water and/or another solvent and exhibits quicktack to, and strong adhesion on, a variety of substrates includingpolymeric substrates.

The compositions, methods, and kits described herein offer significantecological benefits compared to the prior art as well as productscurrently commercialized in particular markets. For example, thecompositions, methods, and kits described herein eliminate the linerbacking which is a waste byproduct of liner-backed pressure sensitiveadhesive labels. This reduces landfill waste and eliminates the energyand carbon emissions from the production of liner backing and theshipment of the material to suppliers and customers.

In addition, the compositions, methods, and kits described hereineliminate the silicone release layer which is either disposed of on theliner backing in liner-backed pressure sensitive adhesive labels or onthe top of the printed layer of linerless pressure sensitive adhesivelabels. In either existing art, the silicone presents an energyintensive manufacturing process and the addition of a petrochemicalderivative product that is unnecessary and eliminated by thecompositions, methods, and kits described herein, thereby reducing thecarbon footprint of the label and the requirement for silicone to beutilized in the label manufacturing process.

SUMMARY OF THE INVENTION

Fluid activatable adhesive compositions and activating fluid(s)compositions for activating the adhesive compositions, which provideimproved liner-free labels capable of adhering to a variety of paper andpolymeric substrates, are described herein.

The adhesive compositions contain at least two polymers with differenthydrophilicities. The more hydrophilic polymer(s) may be referred to as“the hydrophilic polymer” and the less hydrophilic polymer(s) may bereferred to as “the hydrophobic polymer”. The hydrophilic andhydrophobic polymers are selected to allow the at least one hydrophilicpolymer to have a characteristic of quick tack when exposed to ahydrophilic solvent, such as water or other aqueous solvent, while theat least one hydrophobic polymer has a characteristic which enablesstrong adhesion to a paper or polymeric substrate.

The adhesive composition may contain hygroscopic particulate fillerswhich enable fast exhaustion of the activation fluid out of the adhesivewhen applied to a substrate, thereby allowing the hydrophobic polymersof the adhesive composition to achieve strong adhesion of the liner-freelabel to the paper or polymeric substrate. The particulate fillers mayalso provide fast absorption of the activation fluid composition intothe full thickness of the adhesive composition and rapid swelling of notonly hydrophilic, but also the hydrophobic, part of the adhesivecomposition. The particulate fillers may also function as anti-blockingagents when liner-free label media are tightly wound in a roll.

The compositions described herein can quickly go from a non-tacky to atacky state enabling the use of water-activated and/or solvent-activatedliner-free labels for label printing and labeling that require bothquick tack and strong adhesion. In general the tacky characteristics aredrawn from the immediate swelling of the hydrophilic polymers. These inturn swell the entire polymer layer allowing both the hydrophobic andhydrophilic components to wet onto the desired substrate forming anadhesive bond.

The adhesive compositions described herein may be used not only onpaper, cardboard, and metal, but also on glass and plastics commonlyused in commercial applications including, but not limited to,polyethylene terephthalate (PETE, PET, PETG), polyethylene (PE),polystyrene (PS), low-density polyethylene (LDPE), linear low-densitypolyethylene (LLDPE), high density polyethylene (HDPE), polypropylene(PP), polyvinyl chloride (PVC) and polyvinyl chloride films, and TYVEK®,as well as other low energy and thermoplastic substrates.

Kits containing the adhesive formulations are also described herein. Thekit can contain only the adhesive formulation. The kits can contain theadhesive formulation and uncoated labels. The kits can contain paper orsynthetic (polymeric film) labels which have been coated with theadhesive formulation and the activating fluid. The kits can containcoated labels, activating fluid, and an activation apparatus used toapply the activating fluid to the solvent-sensitive adhesive layer. Theactivation apparatus may also be incorporated into a printer or otherlabel dispensing device.

The compositions, methods, and kits described herein offer significantecological benefits compared to the prior art as well as productscurrently commercialized in particular markets. For example, thecompositions, methods, and kits described herein eliminate the linerbacking which is a waste byproduct of liner-backed pressure sensitiveadhesive labels. This reduces landfill waste and eliminates the energyand carbon emissions from the production of liner backing and theshipment of the material to suppliers and customers.

In addition, the compositions, methods, and kits described hereineliminate the silicone release layer which is either disposed of on theliner backing in liner-backed pressure sensitive adhesive labels or onthe top of the printed layer of linerless pressure sensitive adhesivelabels. In either existing art, the silicone presents an energyintensive manufacturing process and the addition of a petrochemicalderivative product that is unnecessary and eliminated by thecompositions, methods, and kits described herein, thereby reducing thecarbon footprint of the label and the requirement for silicone to beutilized in the label manufacturing process.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

“Hydrophilic polymer”, as used herein, refers to one or more polymers inthe adhesive composition having a greater affinity for water than one ormore other polymers in the adhesive composition. Hydrophilicity can bequantified by measuring its partition coefficient between water (or abuffered aqueous solution) and a water-immiscible organic solvent, suchas octanol, ethyl acetate, methylene chloride, or methyl tert-butylether. If after equilibration a greater concentration of the compound isattained in water than in the organic solvent, then the compound isconsidered hydrophilic.

“Hydrophobic polymer”, as used herein, refers to one or more polymers inthe adhesive composition having less affinity for water than one or moreother polymers in the adhesive composition. Hydrophobicity can bequantified by measuring its partition coefficient between water (or abuffered aqueous solution) and a water-immiscible organic solvent, suchas octanol, ethyl acetate, methylene chloride, or methyl tert-butylether. If after equilibration a greater concentration of the compound isattained in the organic solvent than in water, then the compound isconsidered hydrophobic.

“Tack” or “quick tack”, as used herein, refers to instantaneous ornearly instantaneous formation of a bond between an adhesive and surfacewhen brought into light contact for a very short period, e.g., less thanfive second. Tack properties are dependant, at least in part, on theviscoelastic flow characteristics of the polymer adhesive system. In asystem where a volatile solvent-based activation method is beingemployed, it is possible for the system to possess initial tack when theadhesive is in a moist state and no tack (but still be well adhered to asubstrate through adhesive bonding) once the moisture has evaporated orbeen removed. Tack is particularly relevant where bonds must immediatelysustain forces after assembly. Tack forces are particularly significantin maintaining bond strength to low surface energy substrates whenchemical or mechanic bonding processes do not readily occur. Tackmeasurement methods are typically application specific, however theStandard Test Method for Tack of Pressure-Sensitive Adhesives by RollingBall (D3121-06) as developed by the American Society for Testing andMaterials (ASTM) provides a reliable measurement method. In this methoda ball of a fixed size is rolled down a ramp of a fixed height andpropelled onto a tacky label. The distance the ball travels across thelabel provides a measure of tack. “No tack” or “non-tacky” means thatthere is no such instant contact bond or adhesion between the adhesiveand the substrate.

“Blocking” refers to the formation of a bond between the adhesive layerof the label and the top of the label when the label is in roll orstacked form.

“Adhesion” or “adhesive bonding”, as used herein, refers to the longerterm bond between the adhesive and the substrate and/or anotheradhesive. Adhesion, unlike tack, focuses on the bond created between asurface and a substrate (which can also be another adhesive) that is notdependent upon the viscoelastic flow characteristics of the adhesive.

Good adhesive tack (the combination between adhesion and tack) isachieved when the adhesive strength is greater than the cohesivestrength of the adhesive system. A bond of adequate strength can beformed and maintained using adhesive forces, tack forces, or acombination of the two; however, bond formation is not limited by theseforces. Peel strength is a force measure of both tack and adhesiveforces. ASTM Standard D3330 (Standard Test Method for Peel Adhesion ofPressure-Sensitive Tape) provides an accurate measure of peel strength.For a particular substrate, average peel test values range from about100 grams/inch to about 1,000 grams/inch, preferably from about 200grams/inch to about 1,000 grams/inch, more preferably about 400grams/inch to about 1,000 grams/inch to achieve adequate adhesion.

“Open time” as used herein, refers to the amount of time between theactivation of the adhesive and the application of the label to asubstrate.

II. Adhesive Compositions

The adhesive compositions described herein contain a mixture of adhesivematerials, including one or more hydrophilic materials and one or morehydrophobic materials. In one embodiment, the hydrophilic and/orhydrophobic materials are polymeric materials. Each polymer mayrepresent a single polymer or a blend of two or more different polymers.The compositions described herein allow for rapid water penetration intothe hydrophilic material(s) and swelling of the hydrophilic adhesivecomponents for the generation of quick tack followed by theredistribution of the activating solution into the hydrophobicmaterial(s) for longer term adhesion.

Hygroscopic particulate fillers can be incorporated into the adhesivecomposition for the generation of both quick tack and longer termadhesion upon activation by an aqueous or solvent-based solution foradhesion to a variety of substrates, such as paper, cardboard, metal, aswell as glass and plastics (i.e., low energy and thermoplasticsubstrates).

Hygroscopic agents (e.g., particulate fillers) in the adhesiveformulations can modulate the kinetics of water distribution throughoutthe hydrophilic and hydrophobic components of the adhesion compositionto achieve the desired adhesive behavior and performance of theliner-free label. Kinetics may also be modified by the degreehydrophilicity and hydrophobicity of the polymers in the adhesive layer.

Hydrophilic Materials

The hydrophilic materials, e.g. polymeric materials, in the adhesivecompositions described herein provide quick tack, i.e., the initialadhesive force responsible for keeping the label adhered to thesubstrate, for the adhesive compositions. The speed or quickness ofactivation of the hydrophilic material(s) are such that it enables theadhesive, upon application of an activating fluid, to not move (or swim)(or minimize such) once applied to the desired application area of asubstrate. This is of particular utility in high throughput labeloperations where swimming could result in a misplaced label. The polymercomponent(s) are obtained either as aqueous solutions, emulsions,suspensions, or solids, which are diluted or dissolved to the desiredconcentration for incorporation into the adhesive composition.

Suitable materials include, but are not limited to, polyvinyl alcohols,polyvinyl acetates, polyvinylpyrrolidones, polyvinylpyrrolidone-vinylacetate copolymers, polyacrylic acids, polyethylene glycols,poly(2-ethyl-2-oxazoline), polyacrylamide copolymers, ethylene vinylacetates, cellulose derivatives (cellulose acetate, methyl cellulose,ethyl/hydroxyethyl, hydroxymethylpropyl cellulose, etc.), ureas,gelatins, alginates, agars, gum arabics, and other similar materials aswell as combinations of the above materials. Other material(s) havingthe desired short-term adherence characteristic may also be used.Solutions of the hydrophilic polymers described herein generally have apH of 5.0 or greater, preferably 6.0 or greater, more preferably 7.0 orgreater, reflecting an acid number of less than 50, 40, 30, 25, 20, 15,or 10.

In one embodiment, the hydrophilic polymer is apoly(2-ethyl-2-oxazoline), such as those available under the tradenameAquazol® (e.g., Aquazol® 0 200 (mol. wt. 200,000) or Aquazol® 500 (mol.wt. 500,000)), vinyl pyrrolidone/vinyl acetate copolymers, such asPVP/VA E-735 (available from Ashland Chemical Co.) or LUVITEC®(available from BASF), and combinations thereof or CELVOL® 502, apartially hydrolyzed (87-89%) polyvinyl alcohol available from Celanese(Dallas, Tex.). The polymers may be available in solid form, such as drypowders or in solution, such as in ethanol, isopropanol, or water.

The hydrophilic polymers are typically present in an amount from about10% to about 50% by dry weight of the adhesive film, preferably fromabout 20% to about 40% by dry weight of the adhesive film.

A. Hydrophobic Polymers

The hydrophobic adhesive material or materials are typically polymericmaterials providing long-term tack (or adhesion) upon activation by anaqueous or solvent-based solution for adhesion to a substrate. Thesehydrophobic material(s) have the characteristic of being slower wettingthan the hydrophilic material(s) described above and of providinglong-term adhesion of the label to the substrate, especially to ahydrophobic or non-polar surface. The build up to such long-termadhesion may start while the initial adhesive force provided by thehydrophilic adhesive material(s) is also present due to the response tofluid activation. Upon removal or drying of the fluid and long after thehydrophilic adhesive material(s) lose all or some of their adhesivenature, the hydrophobic adhesive material(s) are responsible for thelong term adhesion of the label facestock to the desired substrate.

Due to their hydrophobic nature, most of these polymer adhesivematerial(s) are available as stabilized emulsions, dispersions, and/orsuspensions containing the polymer, surfactants/emulsifiers, stabilizersand other additives. These emulsions are diluted to the desiredconcentrations prior to incorporation into the final adhesive solutions.In a preferred embodiment, the desired overall concentration of thehydrophobic materials is 30% dry solids (weight-to-volume). Thisprovides a sufficiently high amount of solids without increasing theviscosity beyond the acceptable range for many of the desired coatingmethods. Care must be taken with the pH of these emulsions to preventdestabilization or phase separation. The emulsions described hereingenerally have a pH of 5.0 or greater, preferably 6.0 or greater, morepreferably 7.0 or greater, reflecting an acid number of the polymer ofless than 50, 40, 30, 25, 20, 15, or 10.

The hydrophobic polymers are typically present in an amount from about20% to about 80% by dry weight of the adhesive, preferably from about40% to about 80% by dry weight of the adhesive, and most preferably from50% to 75% by dry weight of the adhesive.

Suitable hydrophobic materials include, but are not limited to, naturaland reclaimed rubbers, polyurethanes, non-carboxylated and carboxylatedstyrene-butadiene rubbers, polyacrylates based on the polymerization ofmonomers of methacrylates, methyl acrylate, ethyl acrylate,2-chloroethyl vinyl ether, 2-ethylhexyl acrylate, hydroxyethylmethacrylate, butyl acrylate, butyl methacrylate or combinations of theprevious, polyamides, polyesters, polyolefins, polyolefins containingmaleic anhydride, polystyrenes, polyvinyl esters, polyvinyl ketones,polydiene elestomers, polyiso butylenes, poly butadienes,polychloroprenes, poly styrene acrylics, carboxylated acrylic, styreneand/or butadiene polymers, as well as combinations of the abovematerials. Other material(s) having the desired long-term adherencecharacteristic may also be used.

In one embodiment, the hydrophobic polymer(s) is a carboxylatedstyrene/butadiene copolymer, such as those available under the tradenameStyranol® (e.g., Styranol® ND 430) available from BASF or Rovene®, suchas Rovene® 4049. In other embodiments, the hydrophobic polymer is alatex styrene acrylate, such as those available under the tradenameAcronal®, such as Acronal® A220 or Acronal® 296D. Styranol® is availableas an aqueous dispersion. In a particular embodiment, the hydrophilicpolymer is a poly(2-ethyl-2-oxazoline), such as those available underthe tradename Aquazol® (e.g., Aquazol® 200 (mol. wt. 200,000) orAquazol® 500 (mol. wt. 500,000)), vinyl pyrrolidone/vinyl acetatecopolymers, such as PVP/VA E-735 (available from Ashland Chemical Co.),and combinations thereof and the hydrophobic polymer is a carboxylatedstyrene/butadiene copolymer, such as those available under the tradenameStyranol® (e.g., Styranol® ND 430).

Other suitable hydrophobic polymers include JONCRYL® 2641, a styreneacrylic emulsion supplied at 38.5% wt solids in water available fromBASF (Wyandotte, Mich.); Joncryl JONCRYL® 2646, an acrylic emulsionsupplied at 48.5% wt solids in water available from BASF (Sturtevant,Wis.); JONCRYL® 624, an acrylic emulsion supplied at 48% wt solids inwater available from BASF (Wyandotte, Mich.); JONCRYL® 2330, an acrylicemulsion supplied at 45.5% wt solids in water available from BASF(Wyandotte, Mich.); JONCRYL® ECO 2124, an acrylic emulsion supplied at47.3% wt solids in water available from BASF (Sturtevant, Wis.); UCAR®Latex 6569, an acrylic copolymer emulsion supplied at 57.5% wt solids inwater available from Arkema (Cary, N.C.); VINNAPASS® 401, a poly(vinylalcohol) stabilized vinyl acetate-ethylene copolymer dispersion suppliedat 55% wt solids in water available from Wacker Chemie (Munchen,Germany); AUROREN® AE-202, a waterborne acrylic modified polyolefinsupplied at 30% wt solids in water available from Nippon Paper Chemicals(Tokyo, Japan); ROVENE® 4813 SBR Emulsion, a high gel contentpolymerized latex with 30% bound styrene content supplied at 53% wtsolids in water available from Mallard Creek Polymers (Charlotte, N.C.);DISPERCOLL® C VPLS 2372/1, an aqueous dispersion ofpoly-2-chlorobutadiene-1,3 supplied at 58% wt solids in water availablefrom Bayer Material Sciences (Pittsburgh, Pa.); SNOWTACK® SE 780G, awaterborne tackifier dispersion based on rosin adduction andesterification supplied at 55% wt solids in water available from Lawter(Chicago, Ill.); SNOWTACK® 880G, a waterborne tackifier dispersion basedon rosin and non-rosin resins supplied at 57% wt solids in wateravailable from Lawter (Chicago, Ill.); SNOWTACK® SE 724G, a waterbornetackifier dispersion based on high-grade, stabilized rosin estersupplied at 51% wt solids in water available from Lawter (Chicago,Ill.); and Michem Prime 5931, an ethylene acrylic acid dispersionsupplied at 28% wt in water available from Michelman, Inc. (Cincinnati,Ohio).

B. Hygroscopic Particulate Fillers

Hygroscopic particulate fillers can be added to the composition toenhance the adhesive performance of the hydrophobic and hydrophilicmaterials. The use of such hygroscopic agents is beneficial as a meansto enhance the penetration of water into the adhesive layer on a labelas well as to control the kinetics of adhesive activation based on thedistribution and redistribution of the activation fluid (or solvent)into both the hydrophilic and hydrophobic regions of the adhesive. Inorder for the adhesives to transition from their non-tacky to tackystate, they require a certain amount of water and/or solvent moisture tobe present within the material. The retention of this moisture can beutilized as a mechanism to preserve viscoelastic flow of the polymerlayer and in turn create a tacky label. However, excessive moisture canprevent the contact of the adhesive with the substrate by acting as aphysical barrier to the generation of adhesive interactions resulting inthe migration of the label from the desired application area on asubstrate during down-stream processing. An added benefit of the use ofhygroscopic agents is their ability to reduce the phenomena of‘blocking’ in self-wound rolls of labels having a surface coated withthe adhesive composition described herein.

These hygroscopic particulate filler materials are available ascolloidal suspensions in a variety of solvents or as solids and areincorporated into the final adhesive composition at the desiredconcentrations. Concentrations of the suspensions are typically in therange of 10% to 90% solids (weight of solids in the suspension to volumeof liquid phase of suspension) in either an aqueous or solvent basedsuspension and present in the final dry film in a ratio from 1% to 25%(weight of dry solids in film as a ratio of other components dry weightin film). However, concentrations below or above this range are possibledepending on the composition and/or the desired application.

Care should be taken to prevent the flocculation of these hygroscopicagents during adhesive preparation and storage since these agents areoften micro- and nanoparticles, which are prone to aggregation due totheir high surface area to volume ratios. Generally, particles withinthe particulate fillers may have the largest particle dimension between0.005 μm (micrometers) and 15 μm, more preferably between 0.005 μm and10 μm, and most preferably between 0.005 μm and 5 μm. As used herein,the term “largest particle dimension” refers to the longest lineardimension between two points on the particle.

Methods to ensure the homogenous distribution of these agents insuspension can include the use of agitation, surfactants, temperatureand/or pH. The pre-saturation or treatment of the hygroscopic agentsusing solvents, water, and/or adhesive components is also possible toalter their affinity for different components of the activatingsolution.

Suitable hygroscopic particulate fillers include, but are not limitedto, alumina, alumina gel, boehmite, pseudoboehmite, clay, calciumcarbonate, chalk, magnesium carbonate, kaolin, calcined clay,pyropylate, bentonite, zeolite, talc, silica, silica gel, syntheticaluminum silicates, synthetic calcium silicates, diatomatious earth,anhydrous silicic acid powder, aluminum hydroxide, barite, bariumsulfate, gypsum, calcium sulfate, and organic particles, such ashydrophilic and/or hydrophobic polymeric beads including but not limitedto polyamides, polyethylene, polypropylene, and/orpolytetrafluoroethylene, non-woven microfibers and other similarmaterials as well as combinations of the above materials.

C. Polymer Solvents

Solvent(s) can be added to the composition as means for formulating thehydrophilic and/or hydrophobic materials. For example, solvent(s) can beadded to mirror the composition of the solution of the activating fluidto enhance the rapid swelling of the label and quick tack adhesionforces following the exposure of the adhesive layer to the activatingfluid. By including the chemistry of the activating solution during thedeposition process, the surface of the adhesive can be modified topromote the penetration of the activating solution into the adhesivelayer for activation. Furthermore, the incorporation of solvents,particularly those that are less viscous and/or have higher vaporpressures, allows for the deposition of more consistent and uniformadhesive films on the labels. Furthermore, some solvents may be able toprevent any adverse effects of the adhesive layer deposition process onthe front side of the label, which must remain pristine for optimallabel print quality. Care must be taken to insure that the solventselected does not damage or deform the substrate being coated. In oneembodiment, thermally activated paper is coated with a water basedsolvent system as primary alcohol, glycols, and acetates tend to damageor activate the thermal ink. Solvents may include, but are not limitedto, ethanol, isopropanol, n-propanol, methyl ethyl ketone, toluene,methylene chloride, and/or coalescing agents including polyethyleneglycol, glycol ethers, and fatty alcohols.

D. Activating Fluids

The activating fluid composition provides optimal activation of theadhesive component(s) of the layer of adhesive composition of theliner-free label. The activating fluid composition must penetrate intothe adhesive layer to moisten the hydrophilic and hydrophobic adhesivecomponents without over-wetting the adhesive surface of the label, whichcan compromise adhesive performance. In addition, the activating fluidcomposition needs to be compatible with mechanisms for applyingactivating fluids onto a liner-free label, such as in stand-alonesystems, label printers, labeling lines, or other apparatuses. Theactivating fluid composition should also be safe, non-toxic and complywith the guidelines established by regulatory boards for their intendedpurpose.

The purpose of the activating fluid (or solution) is to introducemoisture into the adhesive layer to allow for the conversion of theadhesive from its non-tacky to tacky state. However, given the selectionof both hydrophilic and hydrophobic adhesive materials, one must accountfor the chemistries of the two or more polymers and the solvent used inthe deposition process for enabling optimal activation. As describedpreviously, the activating fluid needs to penetrate into the hydrophilicregions of the adhesive layer to generate quick tack then redistributeand remain in the hydrophobic regions to maintain ultimate tack andlong-term adhesion.

Upon contact with the adhesive layer, the activating fluid rapidlypenetrate into the adhesive layer causing the hydrophilic regions toswell resulting in the generation of quick tack and increasing thesurface area of the hydrophobic regions without causing the label tobecome slick and slide from the desired area of application. In oneembodiment, the quick tack will result in average peel strength rangesof greater than about 100 grams/inch within about 5 minutes ofapplication to a substrate, preferably an average peel strength ofgreater than about 200 grams/inch within about 2 minutes of applicationto a substrate, more preferably an average peel strength of greater thanabout 200 grams/inch within about 1 minute of application to asubstrate. The activating fluid then distributes into the hydrophobicregions resulting in their swelling and ultimate adhesion to thesubstrate. This adhesion to the substrate results in average peel testvalues in the range from about 100 grams/inch to about 1,000 grams/inch,preferably from about 200 grams/inch to about 1,000 grams/inch, morepreferably from about 400 grams/inch to about 1,000 grams/inch. Theactivating fluid then is removed from the hydrophilic regions eitherinto the hygroscopic filler or by evaporation so that ultimate tack isnot compromised by the presence of excess moisture in the label.

Suitable solvents include, but are not limited to, water; acetone;acetonitrile; lower alcohols (i.e., having from 1-10 carbons) including,but not limited to, methanol, ethanol, isopropyl alcohol, n-propanol,n-butanol, 2-butanol, isobutanol, 2-methy-2-butanol, n-pentanol,n-hexanol, 2-hexanol, cyclohexanol, n-heptanol, n-octanol, n-nonanol,n-decanol; glycols including, but not limited to, propylene glycol,ethylene glycol, and butylene glycol; fatty alcohols (i.e., having morethan 10 carbons) including, but not limited to, undecanol, dodecanol,1-tetradecanol, arachidyl alcohol, docosanol, tetracosanol, hexacosanol,octanosol, triacontanol, cetyl alcohol, stearyl alcohol, andpolycosinol; ketones, such as methyl ethyl ketone; esters, such as lower(i.e., having from 1-10 carbons) acetates including, but not limited to,methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate,isobutyl acetate, sec-Butyl acetate, tert-Butyl acetate,3-methyl-1-butyl acetate; mineral spirits; oils, such as linseed oil andvegetable oil; citrus based solvents, such as limonene, other primary,secondary, and tertiary alcohols, and combinations thereof.

Low volatile solvents, such as ethylene glycol and propylene glycol, areparticularly useful in extending the latency period.

Low surface energy solvents, such as isopropyl alcohol are particularlyeffective in increasing wet out on hydrophobic and/or low surface energysubstrates.

The polymer selection for the adhesive formulation can be such that theactivation solvent required to activate the label is water. However,selecting polymers that only require water to rapidly transition fromnon-tacky to active may not be desirable as the finished labels arehighly vulnerable to blocking due to absorption of atmospheric moisture,causing a transition from the non-tacky state to the tacky state.

Therefore, in one embodiment, the activating fluid contains at least twoor more solvents. The first solvent or component is water or an aqueoussolution which allows for rapid wetting and swelling of the hydrophilicregions of the adhesive to generate the quick tack responsible for theinitial adhesion of the label to the substrate. However, as the water isdrawn into the hygroscopic filler, quick tack is lost and must bereplaced by ultimate or long-term tack, derived from the hydrophobicregions, which exhibit some swelling behavior in water. Thus, a secondsolvent or component is a non-aqueous (non-water) solvent containinghydrophobic chemical moieties which enhances the activation of thehydrophobic regions by increasing the permeability of the activatingfluid into these regions. In a particular embodiment, the non-aqueoussolvent is partly miscible or fully miscible with water. By using amixture of solvents, the swelling of the hydrophilic regions canincrease the surface area of the hydrophobic regions exposed for solventpenetration, resulting in the more rapid generation of ultimate tack. Anoptional third solvent or component, which preferably is a volatilematerial, may be used to aid in the removal of excess moisture from theadhesive layer to promote stronger adhesion. This is in contrast to U.S.Pat. No. 7,943,714, which describes the use of water only, or water plusadditives, such as silicates and/or polymers, as the solvent. However,the use of water alone can be problematic as described above. Thesolvents systems described herein are non-toxic (phthalate free), do notcontain non-volatile materials (e.g., solids), and are low viscosity forspray applications.

In one embodiment, the solvent contains between 5% and 20% of anon-toxic organic solvent in an aqueous solution. Care should be takento match the polymer adhesive layer with suitable solvents that willactivate the layer within the parameters discussed above. In aparticular embodiment, the activation composition is a mixed solventsystem with 1-50% w/w alcohol in water, preferably a 10% w/w mix of analcohol in water. However, any polar solvent with some water miscibilitycontaining hydrophobic chemical moieties may also be used.

The solvent system can be varied for a particular adhesive compositionin order to vary the properties of the adhesive composition. Forexample, the examples below show that the activating solvent can bevaried to correlate with the selected hydrophilic and/or hydrophobicmaterials to achieve the desired performance. Generally, a solvent is aliquid fluid that either solubilizes or swells polymeric components of asolvent sensitive film. A non-solvent is a liquid fluid that does notsolubilize or swell the polymeric components of a solvent sensitivefilm. In one embodiment, non-solvent can be incorporated into theactivation fluid to reduce the overall average peel adhesion of thelabel. In another embodiment solvent with a vapor pressure greater thanthat of water at a given temperature can be incorporated into theactivation fluid to lower the amount of time required to achieveacceptable ultimate adhesion values.

To decrease surface tension, enhance solvent spreading on the adhesivefilm surface, and/or promote activating solvent penetration, surfactantsmay be added to the activating fluid. Surfactants may also help in thedelivery of the activating fluid by allowing for the creation of finermists with smaller particle sizes during atomization (when used to applythe activating fluid to the adhesive layer of a label) which can promoteadhesive activation by increasing the surface area for the interactionbetween the activating solution and the adhesive layer. Classes ofsurfactants that can be used include anionic, cationic, non-ionic andamphoteric surfactants. Specific examples include lecithin, Span™-60,Span™-80, Span™-65, Tween™-20, Tween™-40, Tween™-60, Dynol™ 604 (AirProducts), Surfynol™ (Air Products), Pluronics™ (BASF, Germany),Polysorbates™ (Tween™), Sodium dodecyl sulfate (sodium lauryl sulfate),Lauryl dimethyl amine oxide, Cetyltrimethylammonium bromide (CTAB),Polyethoxylated alcohols, Polyoxyethylene sorbitan, Octoxynol™ (TritonX100™), N,N-dimethyl-dodecylamine-N-oxide, Hexadecyltrimethyl-ammoniumbromide (HTAB), Polyoxyl 10 lauryl ether, Brij™ 721™, Bile salts (sodiumdeoxycholate, sodium cholate), Polyoxyl castor oil (Cremophor™),Nonyiphenol ethoxylate (Tergitol™), Cyclodextrins, Lecithin, orMethylbenzethonium chloride (Hyamine™).

E. Other Additives

Additives may incorporated into activating fluid, such as acids, bases,buffers, antimicrobial agents, stabilizers, emulsifiers, and/ordefoaming agents, as needed for the particular application.

Other additives may be added into the compositions to modulate theperformance of the liner-free labels. These additives may be selectedfor a variety of purposes, such as enhancing water penetration, reducingblocking, increasing quick tack and/or long-term adhesion as well asimproving latency (the time between label activation and application).Potential classes of additives include, but are not limited to, salts,sugars, other carbohydrates, polyelectrolytes, proteins, dry and liquidsurfactants, resins, wetting agents, additive that provide desired layflat properties of the labels, such as humectants, polyethylene glycol,and/or salts, other similar materials as well as combinations thereof.These additives can be incorporated into one or both of the polymercomponents, the polymer solvent, the activating fluid, or combinationsthereof.

In particular, the use of non-volatile solvents, plasticizers,coalescents, oligomers, and/or polymers in the activation may extend theopen time of a given adhesive composition. The additives in theactivation spray should not clog the applicator used to apply theactivation spray and should not require excessive cleanup.

1. Plasticizers

In one embodiment, the activating fluid further contains one or moreplasticizers. Plasticizers can be used to improve long term adhesivebond strength, particularly to polymeric substrates, such aspolyethylene, provided they exhibit good solvency and/or plasticizationof the desired polymer adhesive layer. Plasticization can be describedas the ability for a plasticizer to soften a polymer film. In someinstances, an adequate measure of plasticizer response can be measuredby the ability for a plasticizer to lower the glass transition point(T_(g)) of a desired polymer.

Suitable plasticizers include, but are not limited to, low to mediummolecular weight polyols and diols including, but not limited topolyethylene glycol, propylene glycol, ethylene glycol, other alcoholsincluding, but not limited to, fatty alcohols, adipates, phosphates,azelletes, citrates, butyl cellosolve, polyol polyethers, including, butnot limited to propylene glycol monomethyl ethyl ether, dipropyleneglycol methylethyl ether, dibasic esters, benzoates and related acids,carbonates, lactones, phthalates, other hydrocarbon based oils and othersolvents that are non-volatile at standard temperature and pressure(STP). In one embodiment, the plasticizer is a polyol polyether, such asthose available under the tradename PLASTITILT® and MACOL®. Compoundsmarketed as surfactants can also be used as a plasticizer provided theyprovide the desired properties of no-volatility at operatingtemperatures and exhibit good solvency and/or plasticization of desiredpolymer adhesive layer.

The concentration of the plasticizer or plasticizer(s) is typically fromabout 5% to about 50% by weight of the activation spray. Solvents andsurfactants can also be used to allow miscibility in aqueous solutionsor emulsions. The use of plasticizers can provide quicker tack,particularly on polymeric substrates, and can extend open times fromshort term (less than 90 seconds to) to an indefinite amount of timesignificantly greater than 28 days.

III. Kits

Kits containing the adhesive compositions or the components to preparethe adhesive compositions are described herein. In one embodiment, thekit contains, premixed, the hydrophilic and hydrophobic materials, aswell as any additives. The mixture can be in the form of a solution orsuspension in a suitable solvent. Alternatively, the mixture can be asolid, which is formulated into a solution or suspension by the user. Inthese embodiments, the kit can contain one or more solvents forformulating the adhesive composition. The hydrophilic materials,hydrophobic materials, additives, and/or solvents can be provided inappropriate containers, such as drums or totes. The kit may also containinstructions for preparing the adhesive composition as well asinstructions for applying it to labels. The kit can also contain theactivating solution, which is packaged in a separate container, such asa drum or tote. The activating solution may contain one or moreadditives already dissolved or dispersed in the activating solution.Alternatively, the additives can be added to the activating solutionprior to use.

In some embodiments, the adhesive composition and the activatingsolution are sold to an entity that applies the adhesive composition tolabels and sells the treated labels and the activating solution to thefinal end user. The entity that sells the treated labels and theactivating solution to the final end user can package the labels andactivating solution with a printing/labeling device, fitted with anaftermarket device to activate the labels, used to print the labelsand/or apply them to commercial products.

In another embodiment, finished labels are provided to the finalcustomer to which the adhesive composition has been applied prior topackaging of the labels. The user loads the labels into the appropriateprinting/labeling device, as described above, which has been fitted withthe aftermarket device for activating the adhesive composition. Theaftermarket device applies the activating solution to the label toactivate the adhesive and is reusable. The aftermarket device can bereplaced as needed. Once an end user has acquired the aftermarketdevice, kits containing labels and the activating solution, which ischarged into the aftermarket device, can be purchased by the end user.

In specific embodiments, kits are sold to label coaters/manufacturers.The kits can contain one or more of the following: (1) drums, pales,totes, or other bulk containers containing adhesive to be coated onto aface sheet using a large format web-based coater; (2) drums, pales,totes, or other bulk containers containing activation fluid to berepackaged into refill stations, reusable containers, or disposablecartridges; (3) refill stations, reusable containers, or disposablecartridges containing activation fluid; (4) wide format rolls ofliner-free labels; and combinations thereof. The elements of the kit canbe sold to a single coater/manufacturer or do multiplecoaters/manufacturers.

In other embodiments, kits are sold to the end user. These kits cancontain one or more of the following: (1) a liner-free label with anadhesive on the back side of the substrate, activated by a volatilesolvent fluid sprayed by a single nozzle mounted to retrofit to a labelprinter; (2) a liner-free label with an adhesive on the back side of thesubstrate, activated by a nonvolatile solvent fluid sprayed by a singlenozzle mounted to retrofit to a label printer; (3) a liner-free labelwith an adhesive on the back side of the substrate, activated by anonvolatile solvent fluid sprayed by an array of nozzles mounted toretrofit to a label printer; (4) a liner-free label with an adhesive onthe back side of the substrate activated by a volatile solvent fluidsprayed by an array of nozzles mounted to retrofit to a label printer;(5) a Liner-Free Label with a primer layer on the back side of thesubstrate, with an adhesive applied to the substrate by a single nozzlemounted to retrofit to a label printer; (6) a Liner-Free Label with aprimer layer on the backside of the substrate, with an adhesive appliedto the substrate by an array of nozzles mounted to retrofit to a labelprinter; (7) a Liner-Free Label with a primer layer on the backside ofthe substrate, with an adhesive applied to the substrate by a singlenozzle, and then activated by a volatile solvent fluid sprayed byanother nozzle, mounted to retrofit to a label printer; (8) a Liner-FreeLabel with a primer layer on the backside of the substrate, with anadhesive applied to the substrate by a single nozzle, and then activatedby a nonvolatile solvent fluid sprayed by another nozzle, mounted toretrofit to a label printer; (9) a Liner-Free Label with a primer layeron the backside of the substrate, with an adhesive applied to thesubstrate by an array of nozzles, and then activated by a volatilesolvent fluid sprayed by another array of nozzles, mounted to retrofitto a label printer; (10) a Liner-Free Label with a primer layer on thebackside of the substrate, with an adhesive applied to the substrate byan array of nozzles, and then activated by a nonvolatile solvent fluidsprayed by another array of nozzles, mounted to retrofit to a labelprinter; (11) a Liner-Free Label with no coating on the back side of thesubstrate, with an adhesive applied to the substrate by a single nozzlemounted to retrofit to a label printer; (12) a Liner-Free Label with nocoating on the backside of the substrate, with an adhesive applied tothe substrate by an array of nozzles mounted to retrofit to a labelprinter; (13) a Liner-Free Label with no coating on the backside of thesubstrate, with an adhesive applied to the substrate by a single nozzle,and then activated by a volatile solvent fluid sprayed by anothernozzle, mounted to retrofit to a label printer; (14) a Liner-Free Labelwith no coating on the backside of the substrate, with an adhesiveapplied to the substrate by a single nozzle, and then activated by anonvolatile solvent fluid sprayed by another nozzle, mounted to retrofitto a label printer; (15) a Liner-Free Label with no coating on thebackside of the substrate, with an adhesive applied to the substrate byan array of nozzles, and then activated by a volatile solvent fluidsprayed by another array of nozzles, mounted to retrofit to a labelprinter; (16) a Liner-Free Label with no coating on the backside of thesubstrate, with an adhesive applied to the substrate by an array ofnozzles, and then activated by a nonvolatile solvent fluid sprayed byanother array of nozzles, mounted to retrofit to a label printer; andcombinations thereof.

The kits can include a device which is retrofitted to a label printerwhich prints, activates, and/or applies the labels. The activating fluidcan be supplied in cartridge form which is inserted into or attachedonto the retrofitted device. The cartridge may be removable once thefluid has been exhausted. The cartridge can be refilled by the end useror can be returned to a supplier who provides refilled cartridges. Inother embodiments, the fluid is delivered to the retrofitted device in acontainer that plugs into a reservoir that is contained within theretrofit to the label printer.

In those embodiments, where the label contains a primer layer betweenthe label and the adhesive layer, the primer layer can be applied to thelabel by the label manufacturer who provides the primer-coated labels tothe end user. The end user can then apply the adhesive layer to thelabel using the retrofit to the label printer. As discussed above, theadhesive can be contained in a cartridge form that is removable from theretrofit to a label printer or in a container that plugs into areservoir that is contained within the retrofit to a label printer. Insome embodiments, the back side of the label is uncoated and theadhesive is applied via the retrofit described above (e.g., cartridge orcontainer).

The retrofit can be a device that is mounted to a label applicator orother form of “print-apply” labeling equipment. Alternatively, theretrofit can be a device that is a standalone device with no connectionsto any printing or labeling equipment.

IV. Methods of Making Adhesive Compositions

The hydrophilic and hydrophobic polymers can be packaged individually,along with one or more solvents, and mixed together at a later time.Alternatively, the polymer can be mixed together to form a blend anddissolved or suspended in a solvent in the form of an emulsion,suspension, or solution.

As discussed above, the hydrophilic and hydrophobic polymers can beprovided individually, or as a mixture, in the form of a solid,solution, or suspension. Prior to the preparation of the final adhesivecomposition, all formulations are diluted to the desired concentrationswith distilled water or appropriate organic solvent.

The desired coating concentration of the formulations is between 25% and55% solids (weight-to-volume). Depending on the particular combinationof components in the adhesive compositions, the hydrophobic andhydrophilic adhesive components are mixed together in the appropriateratios followed by addition of the other components. For example, if thehygroscopic particulate filler to be added is in the form of a colloidalsuspension, the polymer mixture can be mixed into this suspension; ifthe hygroscopic agent is a solid, it can be added to the polymermixture. In general, solutions are added in increasing order ofviscosity followed by solids. To ensure the homogeneity of the finalproduct, shear is introduced to the formulation.

V. Methods of Using Adhesive Compositions

The final liner-free label is composed of an adhesive layer and afacestock. Application of the adhesive layer to the facestock is part ofthe manufacturing process that influences the end adhesive performance.

A. Facestocks

Unlike other water and solvent activated labels and adhesive systems,the adhesive compositions described herein can be applied to a varietyof facestocks, with a variety of MVTR of the facestock. Suitablefacestocks include, but are not limited to, paper, top-coated andnon-top-coated grades of direct thermal paper, polymer films, woven andnon-woven synthetic materials, wood, metal films, composite films,plastics, and mylar. In some embodiments, the face stock can be printedon with a suitable printing device. In other embodiments, the adhesiveside of the label can receive dye/ink/pigment from a printing device,for example, printer registration marks.

B. Substrates

The adhesive compositions described herein can be used to adhere coatedlabels to a variety of substrates. Suitable substrates include, but arenot limited to, paper, cardboard, and metal, glass and plastics commonlyused in commercial applications including, but not limited to,polyethylene terephthalate (PETE, PET, PETG), polyethylene (PE),polystyrene (PS), low-density polyethylene (LDPE), linear low-densitypolyethylene (LLDPE), high density polyethylene (HDPE), polypropylene(PP), polyvinyl chloride (PVC) and polyvinyl chloride films, and TYVEK®,as well as other low energy and thermoplastic substrates.

In some embodiments, the adhesive are designed to adhere to a singlespecific substrate but do not adhere to other substrates. In oneembodiment, the adhesive can be designed to have a specific strength ofadhesion and/or mode of failure. For example, for pharmacy bottles, theadhesive formulation can be designed to be clean-peel but have a highpeel strength. This occurs when the adhesive bond between the facesheetand the substrate is the mode of failure of the label. Morespecifically, the adhesive bond has a lower failure point than theconstruct of the facesheet. In other embodiments, the adhesive isdesigned to adhere to a variety of substrates with little or nomodification of the adhesive formulation.

The adhesive composition (or blend) can be applied to the above listedfacestocks utilizing typical web coating methods including, but notlimited to, knife over roll, gravure, reverse-gravure, metering rod,slot die, and air knife coating methods.

The coat weight of the adhesive composition on the facestock is largelydependent upon the end use application of the solvent sensitive adhesivelabel. To reduce cost, coat weights of 3 dry grams of adhesive persquare meter are typically used. However, coat weights up to 25 drygrams per square meter may be also be used.

After the application of the adhesive composition to the facestock web,the remaining water and solvent is extracted from the adhesivecomposition. This may be accomplished using conventional methodsincluding, but not limited to, air flotation oven, web over rollersoven, energy cure methods, and the like. Alternatively, the adhesivecomposition can be designed such that the polymer, polymers, orparticulate filler in the adhesive composition trap excess polymersolvent and/or activation spray, such that the vapor pressure of thecombined system (polymer(s)+spray) is less than that of the spray alone.This allows any overspray that did not make contact with the label toevaporate, yet keeps the label tacky indefinitely. In one embodiment,this can be accomplished by incorporating inorganic salts as particulatefiller into the adhesive formulation.

Optionally, it may be desirable to coat thermally activated paper andfilms. Care must be taken in adhesive selection to ensure that thecomponents formulating the adhesive composition do not contain certainchemistries or solvents that negatively interact with the embeddedthermal dye. In addition, during the drying (or solvent removal)process, the heat or energy from the process should not activate thethermal paper (a processes known as imaging). Sometimes the coating of aweb with an adhesive can induce a phenomenon known as a shape memory orcurling. As it is often important for end applications that labels havelay flat properties, a number of additives can be added to the adhesiveformulation to prevent curl, as described earlier. In addition,mechanical methods can be employed to reduce curl. Also, the addition ofvaporized water (or other liquid vapors) to the non-adhesive coated sideof the label can have dramatic effects in reducing curl.

C. Coated Labels

In one embodiment, the final product is a label having three layers: afirst layer which is printable upon such as by a typical label printer,second layer of face stock material, and then a third layer of adhesivecomposition described herein, e.g., coated on one surface of the facestock, such as a film composed of a blend of hydrophobic and hydrophilicpolymers containing a dispersion of hygroscopic particulate filler andother additives. Preferably, there is a continuous phase composed of ahomogenous mix of all adhesive polymers with a uniform dispersion of thefiller. Alternatively, there is phase separation of the polymersresulting in a film composed of two phases, one rich in the hydrophilicpolymer and one rich in the hydrophobic polymer; this can occur in twodifferent ways, one with a continuous phase of the hydrophobic polymerwith regions of hydrophilic polymer or vice versa. In these embodiments,the filler is dispersed uniformly in both phases or preferentiallylocalized to one of the polymer-rich phases. In some embodiments, thefiller particles are localized to the surface of the film; in others,they are localized to the interface between the paper and the adhesiveor distributed uniformly in the z-axis. In all embodiments, the adhesiveportion of the liner-free label is in a non-tacky state prior toactivation by the activating solution.

The labels can also be designed to indicate product tampering. In oneembodiment, the labels can be designed to leave a residue, such as partof the label, if the label is removed from the packaging/container. Forexample, labels can be applied to a container containing pharmaceuticalproducts. If someone attempts to remove the label, the residue from thelabel remains on the container indicating that the original label hasbeen removed. This may be useful if the label is applied to thecontainer such that if the container is opened, the label is compromisedand leaves a residue behind.

Adhesive compositions containing one or more hydrophilic materials andone or more hydrophobic materials exhibit higher peel strengths thanmaterials containing one or more hydrophilic or one or more hydrophobicmaterials alone. As shown in the examples, compositions containing oneor more hydrophilic materials and one or more hydrophobic materialsexhibited higher average peel strengths and higher peak peel strengthscompared to adhesives containing one or more hydrophilic or one or morehydrophobic materials alone.

EXAMPLES

A series of solvent-sensitive adhesive liner-free labels were preparedin accordance with the teachings above and the following detaileddescription to test adhesion properties. In accordance with theembodiment(s) described above, the solvent-sensitive adhesive agentlayer was coated on 77 g/m² thermal paper. Each formulation'ssolvent-sensitive adhesive agent layer was both (1) prepared at 30%solids and (2) coated using a #24 Mayer rod to achieve a coating dryfilm weight of 10.812 pounds per ream (3000 ft²). Solvent sensitiveadhesive agent layer was dried in a 40° C. oven for about 3 min toachieve a total moisture content of the dried solvent-sensitive adhesiveliner-free label of 5% to 7%.

Adhesive compositions containing one or more hydrophilic materials andone or more hydrophobic materials were prepared and the peel strengthsof the compositions were measured. For comparison, adhesive compositionscontaining only hydrophilic materials or only hydrophobic materials wereprepared and the peel strengths measured. Samples were cut into 1 inchby 9 inch strips as required by the test method. Samples were activatedby the activation spray described in Tables 1-6 sprayed from a handcontrolled spray nozzle just prior to application with approximately 3to 15 mg/in² of activation spray. The sample strips were applied to thepolyethylene and Tyvek substrate by hand by pressing and smoothing thelabel flat. The force required for removal of the sample strips wasmeasured, averaged, and the mode of failure noted in Tables 1-6. Threereplicates of each sample were tested. Samples were tested at a dwelltime of 2 minutes. Dwell time is the amount of time the activated labelis in contact with a substrate. Dwell time does not incorporate theelapsed time between activation and application to a substrate. Peelstrength was measured using ASTM Standard D3330 (Standard Test Methodfor Peel Adhesion of Pressure-Sensitive Tape). The results are shown inTable 2.

The materials used in the examples can be generally categorized ashydrophilic polymers, hydrophobic polymers, hygroscopic fillers and/orpolymers, and plasticizers. Below is a list of materials mentioned inthe examples categorized as such.

Exemplary hydrophilic polymers include CELVOL® 502, a partiallyhydrolyzed (87-89%) polyvinyl alcohol available from Celanese (Dallas,Tex.).

Exemplary hydrophobic polymers include: JONCRYL® 2641, a styrene acrylicemulsion supplied at 38.5% wt solids in water available from BASF(Wyandotte, Mich.); Joncryl JONCRYL® 2646, an acrylic emulsion suppliedat 48.5% wt solids in water available from BASF (Sturtevant, Wis.);JONCRYL® 624, an acrylic emulsion supplied at 48% wt solids in wateravailable from BASF (Wyandotte, Mich.); JONCRYL® 2330, an acrylicemulsion supplied at 45.5% wt solids in water available from BASF(Wyandotte, Mich.); JONCRYL® ECO 2124, an acrylic emulsion supplied at47.3% wt solids in water available from BASF (Sturtevant, Wis.); UCAR®Latex 6569, an acrylic copolymer emulsion supplied at 57.5% wt solids inwater available from Arkema (Cary, N.C.); VINNAPASS® 401, a poly(vinylalcohol) stabilized vinyl acetate-ethylene copolymer dispersion suppliedat 55% wt solids in water available from Wacker Chemie (Munchen,Germany); AUROREN® AE-202, a waterborne acrylic modified polyolefinsupplied at 30% wt solids in water available from Nippon Paper Chemicals(Tokyo, Japan); ROVENE® 4813 SBR Emulsion, a high gel contentpolymerized latex with 30% bound styrene content supplied at 53% wtsolids in water available from Mallard Creek Polymers (Charlotte, N.C.);DISPERCOLL® C VPLS 2372/1, an aqueous dispersion ofpoly-2-chlorobutadiene-1,3 supplied at 58% wt solids in water availablefrom Bayer Material Sciences (Pittsburgh, Pa.); SNOWTACK® SE 780G, awaterborne tackifier dispersion based on rosin adduction andesterification supplied at 55% wt solids in water available from Lawter(Chicago, Ill.); SNOWTACK® 880G, a waterborne tackifier dispersion basedon rosin and non-rosin resins supplied at 57% wt solids in wateravailable from Lawter (Chicago, Ill.); SNOWTACK® SE 724G, a waterbornetackifier dispersion based on high-grade, stabilized rosin estersupplied at 51% wt solids in water available from Lawter (Chicago,Ill.); and Miehem Prime 5931, an ethylene acrylic acid dispersionsupplied at 28% wt in water available from Michelman, Inc. (Cincinnati,Ohio).

Orgasol 3502 D Nat 1 is a polyimide powder available from Arkema(Philadelphia, Pa.) and is generally characterized as a hygroscopicpolymer filler.

Plasticizers, or non-volatile solvents at operating pressures andtemperatures, described in the examples include: Pycal 94, anon-phthalate plasticizer available from Croda (New Castle, Del.);Acrastrip 950, composed of organic esters, wetting agents andbio-solvents available from U.S. Polychemical Corporation (SpringValley, N.Y.); Montasolv PMP, a poly(ether alcohol) plasticizeravailable from SEPPIC (Fairfield, N.J.); and Glycerin is available fromSan Jose Scientific (Santa Clara, Calif.).

Example 1 Effect of Different Plasticizers on Peel Strength of Adhesives

A series of adhesive having the composition shown in Table 1 wereprepared. All percentages are by weight of the composition. PE ispolyethylene. The peel strengths of the adhesive applied to polyethylene(PE) substrates and Tyvek are shown in columns four and six.

TABLE 1 Adhesive compositions and peel strength Activating PE TyvekAdhesive Solution Time (g/in) Time (g/in) [(55% Joncryl 20% IPA, 7.5% 1hr 75 1 hr 20 2641, 45% UCAR Acrastrip 950, 9569) + 12% 5% Pycal 94,Glycerin] + 10% 5% Glycerin Celvol 502 [(55% Joncryl 20% IPA, 7.5% 1 hr80 1 hr 10 2641, 45% UCAR Acrastrip 950, 9569) + 12% 5% Pycal 94,Glycerin] + 10% 5% Glycerin Vinnapass 401 [(55% Joncryl 20% IPA, 7.5% 1hr 100 1 hr 5 2641, 45% UCAR Acrastrip 950, 9569) + 12% 5% Pycal 94,Glycerin] + 5% 5% Glycerin Auroren AE-202 [(55% Joncryl 20% IPA, 7.5% 1hr 20 1 hr 70 2641, 45% Rovene Acrastrip 950, 4813) + 12% 5% Pycal 94,Glycerin] + 10% 5% Glycerin Celvol 502 [(55% Joncryl 20% IPA, 7.5% 1 hr100 1 hr 125 2641, 45% Rovene Acrastrip 950, 4813) + 12% 5% Pycal 94,Glycerin] + 10% 5% Glycerin Vinnapass 401 [(55% Joncryl 20% IPA, 7.5% 1hr 125 1 hr 100 2641, 45% Rovene Acrastrip 950, 4813) + 12% 5% Pycal 94,Glycerin] + 5% 5% Glycerin Auroren AE-202

Example 2 The Effect of Different Additives on the Adhesive Propertiesof Neoprene formulations

A series of adhesive having the composition shown in Table 2 wereprepared. All percentages are by weight of the composition. PE ispolyethylene. The peel strengths of the adhesive applied to polyethylene(PE) substrates are shown in columns four and six.

TABLE 2 Adhesive formulations that vary by additive Activating PE PEAdhesive Solution Time (g/in) Time (g/in) 70% Joncryl 2641, 30% IPA, 7%1 hr 50 24 hr 220 30% [80:20 Montasolve Dispercoll PMP, 8%CVPLS:Snowtack Acrastrip 950 780G] 70% Joncryl 2641, 30% IPA, 7% 1 hr238 24 hr 82 30% [80:20 Montasolve Dispercoll PMP, 8% CVPLS:SnowtackAcrastrip 950 780G] + 5% SiO2 70% Joncryl 2641, 30% IPA, 7% 1 hr 306 24hr 260 30% [80:20 Montasolve Dispercoll PMP, 8% CVPLS:Snowtack Acrastrip950 780G] + 5% Auroren AE-202

Example 3 Effect of Different Tackifiers on Peel Strength

A series of adhesive having the composition shown in Table 3 wereprepared. All percentages are by weight of the composition. PE ispolyethylene. The peel strengths of the adhesive applied to polyethylene(PE) substrates are shown in columns four, six, and eight.

TABLE 3 Adhesive formulations that vary by tackifier Activating PE TyvekPE Adhesive Solution Time (g/in) Time (g/in) Time (g/in) 70% Joncryl 30%IPA, 1 hr 245 24 hr 202 2641, 24% 7% Dispercoll Montasolve CVPLS, 6%PMP, 8% Snowtack Acrastrip 780G 950 70% Joncryl 30% IPA, 1 hr 343  2 hr411 24 hr 238 2641, 24% 7% FSD Dispercoll Montasolve CVPLS, 6% PMP, 8%Snowtack Acrastrip 880G 950 70% Joncryl 30% IPA, 1 hr 274 24 hr 157.72641, 24% 7% Dispercoll Montasolve CVPLS, 6% PMP, 8% Snowtack AcrastripSE724G 950

Example 4 Effect of Different Joncryls on the Peel Strength of theAdhesive

A series of adhesive having the composition shown in Table 4 wereprepared. All percentages are by weight of the composition. PE ispolyethylene. The peel strengths of the adhesive applied to polyethylene(PE) substrates are shown in columns four and six.

TABLE 4 Effect of different Joncryls on peel strength Activating PE PEAdhesive Solution Time (g/in) Time (g/in) 70% Joncryl 2646, 30% IPA, 7%1 hr 12 24 hr — 24% Dispercoll Montasolve CVPLS, 6% PMP, 8% Snowtack780G Acrastrip 950 70% Joncryl 624, 30% IPA, 7% 1 hr 189 24 hr 201.7624% Dispercoll Montasolve CVPLS, 6% PMP, 8% Snowtack 780G Acrastrip 95070% Joncryl 2330, 30% IPA, 7% 1 hr 227 24 hr 126.5 24% DispercollMontasolve CVPLS, 6% PMP, 8% Snowtack 780G Acrastrip 950 70% Joncryl ECO30% IPA, 7% 1 hr 289 24 hr 125 2124, 24% Montasolve Dispercoll PMP, 8%CVPLS, 6% Acrastrip 950 Snowtack 780G

Example 5 Effect of Additives on the Peel Strength of Joncryl/NeopreneFormulations

A series of adhesive having the composition shown in Table 5 wereprepared. All percentages are by weight of the composition. PE ispolyethylene. The peel strengths of the adhesive applied to polyethylene(PE) substrates are shown in columns four and six.

TABLE 5 Effect of additives on the peel strength of Joncryl/Neopreneformulations Activating PE PE Adhesive Solution Time (g/in) Time (g/in)70% Joncryl 30% IPA, 7% 1 hr  54.34 24 hr 4.69 2641, 21.5% MontasolveDispercoll PMP, 8% CVPLS, 3.5% Acrastrip 950 Snowtack 880G, 5% Orgasol3502 70% Joncryl 30% IPA, 7% 1 hr 275 24 hr 115.5 2641, 21.5% MontasolveFSD Dispercoll PMP, 8% CVPLS, 3.5% Acrastrip 950 Snowtack 880G, 5%Auroren AE-202 70% Joncryl 30% IPA, 7% 1 hr 155.87 24 hr 97 2641, 21.5%Montasolve Dispercoll PMP, 8% CVPLS, 3.5% Acrastrip 950 Snowtack 880G,5% MichemPrime 5931

Example 6 Effect of Joncryl Blends on the Peel Strength of AdhesiveFormulations

A series of adhesive having the composition shown in Table 6 wereprepared. All percentages are by weight of the composition. PE ispolyethylene. The peel strengths of the adhesive applied to polyethylene(PE) substrates are shown in columns four and six.

TABLE 6 Effect of Joncryl blends on the peel strength of adhesiveformulations Activating PE PE Adhesive Solution Time (g/in) Time (g/in)25% Joncryl 30% IPA, 7% 1 hr 384 24 hr 525.5 2641, 50% MontasolveJoncryl ECO PMP, 8% 2124, 21.5% Acrastrip 950 Dispercoll CVPLS, 3.5%Snowtack 880G 37,5% Joncryl 30% IPA, 7% 1 hr 194.3 24 hr 525 2641, 37.5%Montasolve Joncryl ECO PMP, 8% 2124, 21.5% Acrastrip 950 DispercollCVPLS, 3.5% Snowtack 880G 50% Joncryl 30% IPA, 7% 1 hr 9.43  6 hr 145.72641, 25% Montasolve Joncryl ECO PMP, 8% 2124, 21.5% Acrastrip 950Dispercoll CVPLS, 3.5% Snowtack 880G

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of skill in the artto which the disclosed invention belongs. Publications cited herein andthe materials for which they are cited are specifically incorporated byreference.

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

We claim:
 1. A fluid activatable adhesive composition for a liner-freelabel comprising at least two polymeric materials with differenthydrophilicities, which are activated by an activating fluid comprisinga cosolvent comprising water, one or more organic solvents, and aplasticizer.
 2. The composition of claim 1, wherein the more hydrophilicpolymer is selected from the group consisting of polyvinyl alcohols,polyvinyl acetates, polyvinylpyrrolidones, polyvinylpyrrolidone-vinylacetate copolymers, polyacrylic acids, polyacrylates, polyethyleneglycols, poly(2-ethyl-2-oxazoline), polyacrylamide copolymers, ethylenevinyl acetates, cellulose derivatives ureas, gelatins, alginates, agars,gum arabics, and combination thereof.
 3. The composition of claim 1,wherein the concentration of the more hydrophilic material(s) is fromabout 10% to about 50% by weight of the adhesive composition in a drystate.
 4. The composition of claim 1, wherein the concentration of themore hydrophilic material(s) is from about 20% to about 40% by weight ofthe adhesive composition in a dry state.
 5. The composition of claim 1,wherein the more hydrophobic polymer is selected from the groupconsisting of natural and reclaimed rubbers, polyurethanes,non-carboxylated and carboxylated styrene-butadiene rubbers,polyacrylics, polyamides, polyesters, polyolefins, polystyrenes,polyvinyl esters, polyvinyl ketones, polydiene elastomers,polyisobutylenes, and combinations thereof.
 6. The composition of claim5, wherein the more hydrophobic polymer is an acrylic polymer orcopolymer.
 7. The composition of claim 1, wherein the concentration ofthe hydrophobic material(s) is from about 40% to about 80% by weight ofthe dry film.
 8. The composition of claim 1, wherein the adhesivecomposition further comprises a hygroscopic particulate filler.
 9. Thecomposition of claim 8, wherein the hygroscopic particulate filler isselected from the group consisting of alumina, alumina gel, boehmite,pseudoboehmite, clay, calcium carbonate, chalk, magnesium carbonate,kaolin, calcined clay, pyropylate, bentonite, zeolite, talc, silica,silica gel, synthetic aluminum silicates, synthetic calcium silicates,diatomatious earth, anhydrous silicic acid powder, aluminum hydroxide,barite, barium sulfate, gypsum, calcium sulfate, organic particlescomprising hydrophilic and/or hydrophobic polymeric beads, non-wovenmicrofibers and combinations thereof.
 10. The composition of claim 8,wherein the concentration of the hygroscopic material(s) is from about1% to 25% by weight of the dry film.
 11. The composition of claim 1,wherein the overall concentration of the plasticizer is from about 2% toabout 50% by weight of the activation fluid.
 12. The composition ofclaim 1, wherein the plasticizer is a low molecular weight polyol. 13.The composition of claim 12, wherein the low molecular weight polyol isa polyol polyether.
 14. The composition of claim 1, wherein the adhesivecomposition further comprises one or more additives selected from thegroup consisting of salts, carbohydrates, polyelectrolytes, proteins,dry and liquid surfactants, resins, wetting agents, humectants,polyethylene glycol, and combinations thereof.
 15. A method for applyingan adhesive liner-free label to a substrate, the method comprisingactivating an adhesive liner-free label comprising an adhesivecomposition comprising at least two materials with differenthydrophilicities with an activating fluid comprising water, one or moreorganic solvents, and a plasticizer and applying the label to thesubstrate.
 16. The method of claim 15, wherein the substrate is selectedfrom the group consisting of paper, cardboard, and metal.
 17. The methodof claim 15, wherein the one or more organic solvents are selected fromthe group consisting of acetone; acetonitrile; methanol, ethanol,isopropyl alcohol, n-propanol, n-butanol, 2-butanol, isobutanol,2-methyl-2-butanol, n-pentanol, n-hexanol, 2-hexanol, cyclohexanol,n-heptanol, n-octanol, n-nonanol, n-decanol, undecanol, dodecanol,1-tetradecanol, propylene glycol, ethylene glycol, butylene glycol,arachidyl alcohol, docosanol, tetracosanol, hexacosanol, octanosol,triacontanol, cetyl alcohol, stearyl alcohol, polycosinol, methyl ethylketone, ethyl acetate, mineral spirits, linseed oil, vegetable oil,citrus based solvents, limonene, and combinations thereof.
 18. Themethod of claim 17, wherein the activating fluid comprises isopropanolat a concentration of 1%-50% by weight of the fluid.
 19. The method ofclaim 18, wherein the activating fluid comprises isopropanol at aconcentration of 5%-20% by weight of the fluid.
 20. The composition ofclaim 15, wherein the overall concentration of the plasticizer is fromabout 2% to about 50% by weight of the activation fluid.
 21. Thecomposition of claim 15, wherein the plasticizer is a low molecularweight polyol.
 22. The composition of claim 21, wherein the lowmolecular weight polyol is a polyol polyether.
 23. The method of claim15, wherein the label comprises a facestock selected from the groupconsisting of paper, top-coated and non-top-coated grades of directthermal paper, polymer films, woven and non-woven synthetic materials,wood, metal films, composite films, plastics, and mylar.
 24. The methodof claim 15, wherein the adhesive side of the label can receivedye/ink/pigment from a printing device.
 25. The method of claim 15,wherein the adhesive composition is applied to the label using atechnique selected from the group consisting of knife over roll,gravure, reverse-gravure, metering rod, slot die, and air knife coatingmethods.
 26. The method of claim 15, wherein the coating weight of theadhesive is from 3 dry grams of adhesive per square meter to 25 drygrams per square meter.
 27. The method of claim 15, wherein the labelcomprises three layers: a first layer which is printable upon, a secondlayer comprising the label face stock, and a third layer comprising theadhesive composition.
 28. The method of claim 15, wherein the labelleaves a residue upon removal indicating product tampering.
 29. Themethod of claim 23, wherein the label comprises paper.